Complex soap lubricating grease

ABSTRACT

A calcium complex soap lubricating grease comprising lubricating oil and calcium soaps, the calcium soap being prepared from fatty acid, calcium hydroxide, sodium phosphates, and sodium borates.

United States Patent Ullmann et al.

[ Sept. 23, 1975 COMPLEX SOAP LUBRICATING GREASE Inventors: DietrichUllmann, Moers;

Hans-Dieter Grasshoff, Hamburg-Kirchwerder, both of Germany Assignee:Deutsche Texaco Aktiengesellschaft,

Hamburg, Germany Filed: Feb. 4, 1974 Appl. No.: 439,203

Related U.S. Application Data Continuation-impart of Ser. No. 251,665,May 9, 1972, abandoned.

Foreign Application Priority Data May 10, 1971 Germany 2122978 U.S. Cl.252/18; 252/25 Int. Cl. ....C10M 3/18; ClOM 5/14; ClOM 7/20; ClOM 7/24Primary ExaminerDelbert E. Gantz Assistant Examiner-l. Vaughn Attorney.Agent, or FirmT. H. Whaley; C. G. Ries; Henry W. Archer [57] ABSTRACT Acalcium complex soap lubricating grease comprising lubricating oil andcalcium soaps, the calcium soap being prepared from fatty acid, calciumhydroxide, sodium phosphates, and sodium borates.

4 Claims, No Drawings COMPLEX SOAP LUBRICATING GREASE CROSS-REFERENCE TOCOPENDING APPLICATION This application is a continuation-in-part ofcoassigned patent application Ser. No. 251,665 filed May 9, 1972 and nowabandoned.

BACKGROUND OF THE INVENTION This invention is concerned with alubricating grease particularly intended for use with automatic orcentralised lubricating systems and which does not undergo appreciablechanges in consistency when used at temperatures above about 200C.

Experience has shown that calcium complex soap lubricating greases usedwith friction bearings harden at high temperatures causing the bearingsto run hot and, in the extreme case, resulting in engine damage.

This hardening can only be explained by assuming that the complexformation of the calcium complex soap lubricating greases is stillincomplete and contin' ues when the temperature of the bearings is above200C. The increase in consistency is observed especially with thosecalcium complex soap lubricating greases exceeding a mole ratio of lowmolecular carboxylic acids of carbon number below 4 to high molecularcarboxylic acids of carbon number above 3, of 5:1.

Solutions to problems of this kind can not be ob tained simply bycombining the known elements of different lubricating greases. In theproduction of lubricating greases, it has been observed again and againthat the solution to a problem is dependent on minor changes incomposition. For instance, the use of an additional component added in aminor amount to greases of different compositions, may lead todifferent, even to opposite, effects with regard to the final product.These circumstances, therefore, led to a number of proposed solutions tothe problems in this field of lubricating greases as described in thepatent literature and to a belief in the unpredictability of the resultsobtained by effecting such variations in composition.

DESCRIPTION OF THE PRIOR ART The prior art to which this inventionrelates is already aware of the patents discussed hereinbelow.

US. Pat. No. 3,170,879 discloses lubricating greases containing purefatty acids only and a very slight excess of calcium hydroxide to reducelocal overheating.

US. Pat. No. 3,186,944 discloses a water-containing multi-purpose greasecomposition, wherein the complex soap contains Ca-hydroxy stearate,and/or Ca-acetate and Ca-carbonate which is produced in situ from urea,besides a Ca(OI-I) excess of from 1 to 8 percent by weight plus from 0.1to 0.5 percent by weight of water. The grease described by the patenteeis completely different from the grease of this invention, since itcontains water whereas that of the invention is an anhydrous one andcannot contain any water since it is used at temperatures ranging abovethe boiling point of water. Furthermore, the excess amount of Ca(OH) inthe grease of the patent is below the Ca(OI-l) excess range claimedhere.

In US. Pat. No. 2,988,507 are proposed sodium soap greases containing anexcess of alkali and, sodium phosphate in order to improve the oxidationresistance and the extreme pressure properties. The patent concerns agrease that is not at all comparable with the grease of this invention,which is employed in other fields of lubrication. The only feature thatmay be deemed pertinent is the addition of sodium phosphates. However,in this invention, sodium phosphate is added only in connection withsodium tetraborate in order to improve the rheological properties of thecalcium grease for high-temperature lubrication, whereas in the case ofthe sodium grease the addition of sodium phosphate is made to improveespecially the pressure properties.

US. Pat. No. 2,861,043 concerns alkaline earth complex soap greases,preferably calcium complex soap greases, containing calcium salts ofhigh molecular and low molecular fatty acids and inorganic salts (10 to50 percent by weight of the complex soap). The inorganic saltscontemplated therein include alkaline earth metal silicates. In column2, lines 66 ff., it is stated that other possible additives to thethickening system may include Na PO Na I-IPO and Nal-I PO potassiumphosphate, sodium borate, potassium borate. There is a minor excess ofsaponifying agent (hydrated lime) present. However, by recalculating theexamples, it is shown to range below the value of 10 percent by weightof Ca(Ol-l) excess claimed herein as the lower limit.

German Offenlegungsschrift No. 1,444,926 describes a process forproducing a complex grease proposing in combination the use of alow-molecular and a highmolecular acid as well as of a common soapthickener and further proposing the addition of aluminium oxides oraluminium hydroxides to the complex grease. The thickener is then workedup to a complex grease.

German Pat. No. 850,051 mentiones a process for producinghigh-pressure-stable, consistent lubricating greases based on oils andsoaps, minor amounts of different inorganic salts being added to theconsistent greases.

German Pat. No. 1,044,328 describes lubricating oils which are obtainedfrom synthetic oils or mineral oils with a certain content of a complexmetal soap. The complex metal soap should contain at least one metalsoap of at least one high-molecular monocarboxylic acid and at least onelow molecular monocarboxylic acid. British Pat. No. 875,732 discloses alubricating grease mixture of lubricating oil, an inorganic gellingagent, and a small amount of a finely distributed alkaline earth salt ofa carboxylic acid containing from 1 to 10 carbon atoms, German Pat. No.1,594,587 proposes a lubricating grease based on mineral oil or on asynthetic lubrication liquid and organobentonite in order to solve thisproblem, the lubricating grease containing a carboxylic acid ofhigh-molecular weight and of low molecular weight, both acids beingcapable of forming alkaline earth metal salts.

It is already known to produce practically anhydrous calcium soaplubricating greases by co-using calcium acetate, the greases comprisingdropping pour temperatures up to about 300C. The term calcium complexsoap grease" has become an acceptable term for such lubricating greases.These greases substantially consist of lubricating oil and aconsistency-giving thickening agent, that is, calcium complex soap.Hereinafter, the term lubricating oil is used for mineral oils, fattyoils, synthetic oils, and for mixtures of agents of one or more of thesematerials. Fatty oils" are those greases and oils originating from faunaand flora which, substantially consist chemically of mixed glycerineesters of higher fatty acids having an even carbon number. The productsobtained by chemical conversion, e.g., converted esters and partialsaponification are related to this category of substance. The group ofsynthetic oils includes hydrophobic substances of liquid to pastyconsistency, containing carbon, hydrogen, and oxygen. To this groupbelong, for example, those waste products from the production of alkylbenzenes which serve as wash raw materials basis, e.g., mixtures ofcompounds like diaryl-alkane, dialkyl benzene, aromates with longchainalkyl groups, etc. Beside the calcium soaps of normal animal, vegetable,or synthetic fatty acids, re spectively, having a carbon number above 3,the calcium complex soap contains calcium salts of fatty acids having acarbon number below 4, as well, especially calcium acetate. These fattyacids concern aliphatic saturated and unsaturated acids having branchedand unbranched structures. Because of their high dropping points, thecalcium complex soap greases are intended for lubrication uses at hightemperatures. In practice, it was noted that the calcium complex soapgreases often failed in the lubrication of antifriction bearings becauserunning dry took place, a factor independent of the temperature of thebearing. The term running dry means that all lubricant between thetouching, rolling or sliding parts has worn away, i.e., the bearing hasrun dry. This running dry causes overheating due to friction andusually, in consequence, a ruined or burned up engine.

It is not known which of the properties of a lubricating grease causesfailure by running dry. Apparently, the concurrent forces of rheology ofa lubricating grease and of its surface activity play an important but 7still unknown part.

While this running dry of antifriction bearings can be observed inpractice, it can be observed also on test runs. TheSKF-Anti-Friction-Bearing-Lubrication- Testing Machine, according toGerman Technical Publication DIN 51 806, gives a limited bench test. Thelubricating grease is tested under radial stress in two equalself-aligning roller bearings in said testing machine within apredetermined test time. A test-run B is conducted at 1500 rpm and underadditional heating conditions.

SUMMARY OF THE INVENTION Unexpectedly, it has now been found that it ispossible to produce a calcium complex soap lubricating greasesubstantially consisting of lubricating oil and calcium soapscharacterized by an amount of calcium in the form of calcium hydroxideexceeding by from 10 to 60 percent by weight the amount required forsaponification of those normal fatty acids or soap formers having acarbon number about 3 percent therein. An excess of from 30 to 40percent by weight of calcium in the form of calcium hydroxide ispreferred.

DISCLOSURE In a preferred embodiment of the invention a calcium complexsoap lubricating grease, from 0.1 to 4.0 percent by weight of a saltmixture based on the total weight of the lubricating grease are addedduring the process of production. The salt mixture consists ofphosphates and borates of the alkali group of the periodic system ofelements. Adding the salt mixture, especially in the form of sodiumsalts, to the calcium complex soap lubricating grease leads to animprovement of special properties of the complex soap lubricatinggrease. It is to be understood that sodium phosphate means sodium saltsof the o-phosphoric acid (H PO and of polymer phosphoric acids obtainedtherefrom by heating, all acid-hydrogen atoms being substituted bysodium. Sodium borate is to be understood as salts corresponding tosodium phosphates. The salts may either contain crystal water or can befree of it. In the salt mixture, the ratio of sodium phosphate to sodiumborate can vary from 1:4 to 4: 1.

The improved calcium complex soap lubricating grease is especiallyadapted for lubricating antifriction bearings for high temperaturesoperation. For example, the calcium complex soap lubricating greases ofthe subject invention are suitable as antifriction bearing greases atbearing temperatures up to 220C.

The examples below illustrate in non-limiting fashion the presentinvention:

EXAMPLE I 200 kg (kilograms) of lubricating oil having a viscosity of 41cSt/50C. are brought to a temperature of from about 50C to 60C. in avessel with a stirring means. 63 kg of an animal fatty acid soap formerhaving a neutralization number 202 and 88.5 kg of an animal neutralgrease having a saponification number of 196 are introduced thereinto ina melted state. After adding 3 to 4 liters of water, 27.8 kg of calciumhydroxide, slurried in 40 kg of lubricating oil, and 59.3 kg of calciumacetate, slurried in kg of lubricating oil, are added to the batch.Then, further a mix of 5 kg of sodium o-phosphate and 5 kg of boraxdissolved in water is added. Upon the temperature of the contents of thevessel increasing to between C. to 170C., an additional 428.4 kg oflubricating oil are added. Subse quently, the temperature of the batchis further increased to 250C. thereby forming the complex soap. Aftercooling off and homogenizing, a calcium complex soap grease having apenetration range of from 265 to 295 and having a dropping point ofabout 300C. according to German technical publication DIN 51 806 on theSKF-Antifriction-Bearing-Grease-Testing Machine. Even, after having beenstored for a year, the grease did not show any appreciable change in itscharacteristics, especially as to the pentration and to the droppingpoint.

EXAMPLE II 150 kg (kilograms) of a naphthene based mineral oil of aviscosity of 50 cSt/50C. are heated together with 125 kg of oleic acidsoap former in a vessel, as mentioned before, to a temperature of 60C.After reaching this temperature, 46.7 kg of calcium hydroxide, slurriedin 60 kg of mineral oil. 41.3 kg of acetic acid, 6.5 kg sodiumo-phosphate, and 2.5 kg of borax dissolved in water are added one afterthe other to the vessel. The vessel temperature then is increased to200C., followed by the addition of 567 kg of mineral oil, the mineraloil being adjusted to a temperature of 120C. by a heat exchanger.

To form the complex soap, the temperature of the mixture is increased to255C. After cooling the grease to a temperature of about 25C. followedby homogenization, a lubricating grease of NLGI-Class 2 is obtainedhaving a dropping point of about 300C.

EXAMPLE III kg (kilograms) of a fatty acid soap former of animal origin(hardened blubber fatty acid) with a saponification number of 208 aresaponified by adding 28.7 kg of calcium hydroxide in the presence of 350kg of a paraffin base mineral oil having a viscosity of 40 est/50C., ina vessel at a temperature of 75C. This is followed by adding thereto 75kg of calcium acetate and a mixture of 8.3 kg of sodium o-phosphate andof 3.9 kg of borax dissolved in water then, the temperature of thecontent of the vessel is increased to 250C.,

to form the complex soap. At a temperature of 175C.,

teristics after having been stored for one year.

6 total composition, of a complex of calcium soap of a normal fattyacid, or of a soap former having more than 3 carbon atoms in themolecule, and of a calcium salt of a fatty acid having from 1 to 3carbon atoms wherein the ratio of the weight of said normal fatty acidor salt former to said fatty acid having less than 3 carbon atoms rangesfrom about 2 to 1 to about 3 to l; and 0.1 to 4 percent by weight of asalt mixture of alkali phosphates and alkali borates, Ca (0H), beingpresent in said lubricating grease in an amount which exceeds by to 60percent by weight that necessary for the saponification of said normalfatty acid, or said soap former having more than 3 carbon atoms in themolecule. 2. The composition of claim 1, wherein the excess of Ca(Ol-I)ranges from to percent.

3. The composition of claim 1, wherein said salt mixture consists ofsodium phosphates and sodium borates.

SHELFLIFE OF SEVERAL CALCIUM COMPLEX SOAP LUBRICATING GREASESCOMPOSITIONS IN WEIGHT PERCENT Tallow Ca(OH l. A lubricating greasecomposition effective as an antifriction grease at temperatures up to220C, consisting essentially of a major amount of a lubricating oil; offrom about 20 to 35 percent by weight, based on the No. Talgol fattyacid Ca-acetate Excess Shelflife Borax Na-phosphate SNOZO" 9041" Ca(OH)afler 3 yrs.

in wt.%

07 I very strongly (Ex. V11) 6.0 6.0 1.7 6.0 80.3 7 hardened 08 1 (Ex.V) 6.0 6.0 2.18 6.0 79.82 37.5 little hardened 09 6.0 6.0 2. I 8 6.00.34 0.68 78.80 37.5 no change 10 6.0 6.0 1.7 6.0 80.3 7 very stronglyhardened 1 1 6.0 6.0 2.18 6.0 79.82 37.5 little hardened 12 6.0 6.0 2.186.0 0.34 0.68 78.80 37.5 no change 68 (Ex. V1) 6.0 6.0 2.51 6.0 79.49 60little hardened 69 6.0 i 6.0 2.51 6.0 1.5 1.5 76.49 60 no' change 70 6.06.0 2.51 6.0 2.0 2.0 75.49 60 no change 88 very strongly (Ex. IV) 6.06.0 1.57 6.0 80.43 hardened "SN0 20 Solvent Neutral Oil. parafllnic 9041Machine Oil Rufl'lnute. nuphthenic We claim: 40

4. The composition of claim 1, wherein said salt mixture consists ofsodium phosphates and sodium borates in the ratio of weight of from 1 4to 4:1.

* IIK

1. A LUBRICATING GREASE COMPOSITION EFFECTIVE AS AN ANTIFIRICTION GREASEAT TEMPERATURE UP TO 220*C, CONSISTING ESSENTIALLY OF A MAJOR AMOUNT OFA LUBRICATING OIL, OF FROM ABOUT 20 TO 35 PERCENT BY WEIGHT, BASED ONTHE TOTAL COMPOSITION, OF A COMPLEX OF CALCIUM SOAP OF A NORMAAL FATTYACID, OR OF A SOAP FORMER HAVING MORE THAN 3 CARBON ATOMS IN THEMOLECULE, AND OF A CALCIUM SALT OF A FATTY ACID HAVING FROM 1 TO 3CARBON ATOMS WHEREIN THE RATIO OF THE WEIGHT OF SAID NORMAL FATTY ACIDOR SALT FORMER TO SAID FATTY ACID HAVING LESS THAN 3 CARBON ATOMS RANGESFROM ABOUT 2 TO 1 TO ABOUT 3 TO 1, AND 0 TO 4 PERCENT BY WEIGHT OF ASALT MIXTURE OF ALKALI PHOSPHATES AND ALKALI BORATES, CA (OH)2 BEINGPRESENT IN SAID LUBRICATING GREESE IN AN AMOUNT WHICH EXCEEDS BY 10 TO60 PERCENT BY WEIGHT NECESSARY FOR THE SOPONIFICATION OF SAID NORMALFATTY ACID, OR SAID SOAP FORMER HAVING MORE THAN 3 CARBON ATOMS IN THEMOLECULE.
 2. The composition of claim 1, wherein the excess of Ca(OH)2ranges from 30 to 40 percent.
 3. The composition of claim 1, whereinsaid salt mixture consists of sodium phosphates and sodium borates. 4.The composition of claim 1, wherein said salt mixture consists of sodiumphosphates and sodium borates in the ratio of weight of from 1 : 4 to4:1.